An air/fuel mixture flows through the connecting piece from the carburetor to the combustion chamber during operation of the internal combustion engine. A portion of the fuel, especially long-chain hydrocarbons, deposits on the inner wall of the connecting piece and forms a fuel film. Fuel can also collect in the expansion fold of the connecting piece and this fuel can reach the intake channel in an uncontrolled manner because of movements of the work apparatus and can lead to a change of the mixture. These uncontrolled mixture changes can lead to disturbances especially in engines having a low power/weight ratio.
A connecting piece between a carburetor and the combustion chamber of a cylinder is disclosed in U.S. Pat. No. 4,711,225. This connecting piece is made of elastic material and has an expansion fold. A knurling is provided in a region of the connecting piece in order to prevent the fuel film, which has deposited on the inner wall of the connecting piece, from suddenly and uncontrollably reaching the combustion chamber. The knurling is intended to prevent the formation of an uninterrupted fuel film.
It has been shown that the collection of fuel in the connecting piece and the sudden entrainment of the fuel into the combustion chamber is also influenced by the flow velocity in the connecting piece.